have (one's) doubts (about someone or something)
To be wary or uncertain of someone or something. I know you really love this neighborhood, but I have my doubts. I do have my doubts about Brian—he just seems untrustworthy to me.
have your ˈdoubts (about something)
have reasons why you are not certain about whether something is good or whether something good will happen: I’ve had my doubts about his work since he joined the company.It may be all right. Personally, I have my doubts.